Role of transcriptional factors Sp1, c-Rel, and c-Jun in LPS-induced C/EBPd gene expression of mouse macrophages

Transcription factor C/EBPs are involved in the regulation of various cellular responses. Here, it was suggested that C/EBPd gene was activated by lipopolysaccharide (LPS) through transcription factors Sp1, c-Rel, and c-Jun. Assay of the luciferase reporter vectors containing a 5'-deletion of the C/ EBPd gene promoter indicated that a LPS-responsive element was positioned between - 345 and - 35 bp of mouse C/EBPd gene promoter. Transcription factors Sp1, c-Rel, and c-Jun bound to this region were identified using both in vivo chromatin immunoprecipitation and in vitro DNA-protein binding assays. LPS enhanced the proteins and DNA binding capacities of c-Rel and c-Jun, and the downstream Sp1 site was essential for LPS-induced C/EBPd gene. Treatment of cells with ERK/JNK/p38 inhibitors or NF-kB inhibitor inhibited the LPS-induced C/EBPd gene expression by inhibiting c-Jun, c-Rel, and p300 binding to DNA. Our findings provide a better understanding of LPS-induced C/EBPd gene expression.